1. Field of the Invention
The present invention relates to a compaction vehicle used in such a compaction construction of a road surface.
2. Description of the Related Art
A compaction vehicle (for example, see FIG. 1 of Japanese Patent Laid-Open Publication No. 2002-342609) such as a compaction roller and a vibrating roller compacts a road surface by a compaction wheel, repeatedly moving forward and backward at a comparatively low speed. In a compaction construction by compaction vehicle, although there is a case that a vehicle running speed is made different according to such a kind of road surface material (such a kind of asphalt composite material), a temperature of the road surface material, an outside air temperature, a kind of vehicle, and a construction condition, a important matter in any running speed is to run the vehicle at a constant speed so that no variation occurs in a compaction density of the road surface.
Normally, near a driver's seat of a compaction vehicle is provided a forward/backward lever with which the vehicle stops running at a neutral position, moves forward if tilting the lever forward from the neutral position, and moves backward if tilting the lever backward. A running speed is adjusted by the forward/backward lever, and in proportion to a tilting angle from the neutral point, the running speed is designed to increase. Accordingly, in order to run the vehicle at an arbitrary speed, the forward/backward lever is shifted at an appropriate position.
In running a compaction vehicle at a constant speed, in case of only a moving forward or backward, there is no problem because it suffices to once shift a forward/backward lever to an appropriate tilting position as described before. However, because there is a need for repeatedly moving the compaction vehicle in a normal compaction construction as described before, it is necessary in this case for an operator to accurately stop the forward/backward lever again and again at a predetermined tilting position of a forward side and that of a backward side in order to run the vehicle at a constant speed. This accurate lever operation is difficult even for a skilled operator, and it can be said that a strict constant running is extremely difficult in effect.
Consequently, there is a need for a compaction vehicle that can be easily driven at a constant speed even in a case of repeatedly moving forward and backward.